XFS null files

XFS null files

[Jeff Briggs]

Hello.

I've just lost data to XFS, with the files full of nulls. I've found
posts dating back over two years about such data losses. I'm using
linux 2.6.17 with xfsprogs 2.8.10.

emacs claims to fsync on write, yet still I lost data, the faq
suggests I should not have if this is so?

Is this likely to be fixed soon, or should I switch file system?

Many thanks.

Re: XFS null files

[Iustin Pop]

On Sun, Aug 06, 2006 at 08:32:49PM +0100, Jeff Briggs wrote:
> Hello.
> 
> I've just lost data to XFS, with the files full of nulls. I've found
> posts dating back over two years about such data losses. I'm using
> linux 2.6.17 with xfsprogs 2.8.10.
FWIW, I've never lost files since disabling write cache on disks.
> 
> emacs claims to fsync on write, yet still I lost data, the faq
> suggests I should not have if this is so?
Have you disabled the write cache of your storage, or is your storage
battery-backed?

Iustin Pop

Re: XFS null files

[Russell Cattelan]

Jeff Briggs wrote:

> Hello.
>
> I've just lost data to XFS, with the files full of nulls. I've found
> posts dating back over two years about such data losses. I'm using
> linux 2.6.17 with xfsprogs 2.8.10.

Check to see if you have this change
http://oss.sgi.com/cgi-bin/cvsweb.cgi/xfs-linux/xfs_vnodeops.c.diff?r1=1.675;r2=1.676;f=h

I helps reduce the null file problem.

>
> emacs claims to fsync on write, yet still I lost data, the faq
> suggests I should not have if this is so?
>
> Is this likely to be fixed soon, or should I switch file system?

Any caching file system could potentially loose data, XFS just happens to
get the file size correct so you end up with a file that is nothing but a
hole. Other file system would probably just give you an empty file.
Either way data in cache always has the potential for being lost.
Running xfs in full sync mode would be safest but you loose many performance
advantages... so it always a trade off of performance vs data integrity.

>
> Many thanks.
>

Re: XFS null files

[Jeff Briggs]

On 06/08/06, Russell Cattelan <cattelan@thebarn.com> wrote:
> Check to see if you have this change
> http://oss.sgi.com/cgi-bin/cvsweb.cgi/xfs-linux/xfs_vnodeops.c.diff?r1=1.675;r2=1.676;f=h
>
> I helps reduce the null file problem.

i do not.

> > emacs claims to fsync on write, yet still I lost data, the faq
> > suggests I should not have if this is so?
> >
> > Is this likely to be fixed soon, or should I switch file system?
>
> Any caching file system could potentially loose data, XFS just happens to
> get the file size correct so you end up with a file that is nothing but a
> hole. Other file system would probably just give you an empty file.
> Either way data in cache always has the potential for being lost.
> Running xfs in full sync mode would be safest but you loose many performance
> advantages... so it always a trade off of performance vs data integrity.

it's really ugly how the default is not safe. i didn't have my write
cache disabled, but it is now.

thanks for the responses.